The present invention relates to metal coated powders containing silica precursors. These powders can be mixed with solvents to form colloidal dispersions of the metals. These dispersions, in turn, can be used to form coatings having the metals dispersed in silica-containing matrices.
The use of silica-containing ceramic coatings on substrates such as electronic devices is known in the art. For instance, Haluska et al. in U.S. Pat. Nos. 4,749,631 and 4,756,977 disclose processes for forming silica coatings on electronic substrates wherein solutions of silica precursor resins are applied to substrates followed by heating the coated substrates to form the ceramic coating. These references, however, do not describe the inclusion of metals within the coating.
The use of metals within ceramic matrices are also known in the art (i.e., "cermets"). For instance, Ritchie in U.S. Pat. No. 4,640,860 teaches an optical recording coating comprising a metal disposed in a dielectric matrix. This coating, however, is not formed using the materials and methods of the present invention.
Haluska et al. in U.S. patent application Ser. No. 08/221,594, filed Apr. 4, 1994, teach metal containing ceramic coatings derived from solutions of silica precursors and metals. The solutions used therein, however, are not formed by the process of the present invention.
The present inventors have now discovered that metals can be deposited on powders containing silica precursors, that these powders can be dissolved to form colloidal dispersions of metal in silica precursor solutions, that these solutions can be gelled and that these gels can be converted to silica-containing ceramics with the metals dispersed therein.